Laminate composite material

ABSTRACT

A laminate composite material comprises a layer of an open weave supporting fabric having a layer of breathable resin adhered thereto by an extruded layer of a thermoplastic resin blended with a high temperature volatile particulate. The resultant composite material is substantially impervious to air and water and permeable to water vapor and having a water vapor transmission rate exceeding one (1) perm of water vapor.

[0001] This is a divisional of utility patent application Ser. No.09/399,890 filed Sep. 21, 1999.

FIELD OF THE INVENTION

[0002] This invention relates generally to a laminate composite materialhaving a water vapor transmission rate (WVTR) exceeding one (1) perm ofwater vapor where perm (permeance) is in grains/hr. ft.² in.Hg. Moreparticularly, the invention is directed to a laminate composite materialwhich substantially blocks the flow of air and water, but which allowsthe transmission therethrough of water vapor or moisture vapor. Thecomposite material includes a layer of open weave supporting fabric anda film of a breathable resin wherein the layer and the film are adheredto one another by a high temperature volatile particulate added to athermoplastic resin wherein the resultant composite material has a watervapor transmission rate exceeding one (1) perm of water vapor.

BACKGROUND OF THE INVENTION

[0003] It is known that breathable building wraps, also referred to ashousewraps, are used and provide advantages in the construction of walland roof assemblies. These housewrap materials improve energy lossthrough reduction of air infiltration as well as acting as a weatherbarrier by preventing water intrusion into the building. It is arequirement that these materials are breathable, as defined by a minimumlevel of water vapor transmission rate (WVTR). Two popular materialsthat are manufactured for housewrap that achieve the combination of abarrier to water intrusion and air infiltration while remainingpermeable to moisture vapor are a flash spunbonded polyolefin that maybe obtained from DuPont under the name Tyvek™. A second material is amicroporous polyolefin film composite and may be obtained from SimplexProducts under the trademark “R-Wrap™.”

BACKGROUND OF THE PRIOR ART

[0004] It is known to use porous polyolefin films composites inhousewrap applications. Housewrap materials must be permeable to gasesas to allow water vapor to escape from the wall to which the film issecured. Otherwise, condensation of the water vapor trapped inside thewall may occur which leads to rotting and the growth of fungus, mold andmildew which may damage the wall. The film must be sufficientlyimpervious to air to insulate the wall against wind and water intrusion.Further, the film must have adequate tensile and physical propertiessuch as break strength, elongation, tear strength, shrinkage andpuncture strength to avoid damage during installation.

[0005] It is also known to prepare porous polyolefin films by stretchinga precursor film filled with calcium carbonate. “Breathable” films whichare gas/vapor permeable and liquid impermeable have been described inU.S. Pat. No. 4,472,328, assigned to Mitsubishi Chemical Industries,Ltd. The Mitsubishi patent describes a breathable polyolefin filmprepared from a polyolefin/filler composition having from 20 percent to80 percent by weight of a filler such as a surface treated calciumcarbonate. A liquid or waxy hydrocarbon polymer elastomer such as ahydroxy-terminated liquid polybutadiene was found to produce a precursorfilm that could be monoaxially or biaxially stretched to make a filmbreathable. The breathable film described by Mitsubishi is alsodescribed in Great Britain Patent No. 2,115,702, assigned to KaoCorporation. The Kao patent further describes a disposable diaperprepared with a breathable film as disclosed by the Mitsubishi patent.The breathable film is used as a backing for the diaper to containliquid.

[0006] It is also known to laminate porous polyolefin films, alsoreferred to as microporous films, to open mesh fabrics as described inU.S. Pat. No. 4,929,303 assigned to Exxon Chemical. In the Exxon patentan open mesh fabric known under the trade designation CLAF, asmanufactured by Amoco Fabrics, and a microporous film known under thetrade designation Exxaire™, as manufactured by Exxon Chemical, arelaminated together, without the addition of an adhesive. Wherein thefabric is heated on a hot roller and then pressed into contact with theunheated film creating a bond between the two layers. This technique isknown in the art as “thermo bonding.”

[0007] It is also known to bond or adhere two or more layers one toanother with the use of various mastics or adhesive coatings. But use ofmost known adhesives, mastics and coatings when applied between a fabriclayer and a microporous film seal the micropores of the film renderingit non permeable to water vapor and thus it becomes non functional andtotally ineffective.

[0008] Further, as described in the Exxon patent an open mesh fabric isrequired in the composite to add strength and maintain permeability towater vapor and allow free passage of water vapor through themicroporous film and continue generally unimpeded through the openingsin the fabric.

[0009] It is known in the industry that when adhesive coatings areapplied to open mesh fabrics it is possible for the adhesive to migratethrough the openings in the fabric. This uncontrolled migration ofadhesive, bonds each internal “top” layer to the succeeding “bottom”layer as the completed composite is rolled up on a take up reel. Hence,each concentric layer is bonded to the next on the accumulated roll andcannot later be unrolled. This is a highly undesirable conditionunrolled condition known in the art as “blocking.”

[0010] It is known to add high temperature volatile materials, sometimesreferred to foaming agents to thermoplastics for the purpose of creatingclosed gas cells resulting in the lowering of the density of thefinished material. This is a common practice in the injection moldingprocess but not common in the extrusion film process.

SUMMARY OF THE INVENTION

[0011] There has surprisingly been discovered an adhesive material andprocess for applying same that would bond microporous films to open meshfabrics that would avoid sealing of the micropores and thus maintain thehigh permeance (WVTR). Said adhesive material also avoid “block” of theinternal layers within the rolled up composite.

[0012] Also contemplated is a process for preparing the laminatedcomposite. The process comprises steps of specially preparing apolyolefin resin extruding that resin through a die to form an adhesivelayer between a microporous film and an open mesh fabric. The resultingcomposite would be substantially impervious to water and air yet havinga high water vapor transmission rate (WVTR) and would exceed a minimumof 1 perm of water vapor. The invention utilizes conventional equipmentthat is well known in the art.

[0013] The laminate composite according to the present invention isespecially well suited as a building wrap or roof underlayment but couldbe useful in other industrial and consumer applications.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The laminate construction material according to the presentinvention comprises a layer of an open weave supporting fabric adheredto a microporous or a monolithic film by a layer of dry adhesive slitfilm that is heated and then introduced between said layers thus actingas a bonding agent. The film layer may be microporous or monolithic,being substantially impervious to water and air and having a water vaportransmission rate greater than 1 perm. A microporous film ismanufactured by conventional methods of extrusion or casting apolyolefin resin with added fillers followed by monoaxially or biaxiallystretching as to form interconnected voids. A preferred microporous filmis designated under the name Exxaire™ and obtained from Exxon Chemical(now Tredegar).

[0015] The composite material of the present invention may be preparedby utilizing conventional extrusion and laminating equipment. Theprepared resin with a high temperature volatile particulate additive ismelted in a conventional extruder and extruded through a die to form alayer of molten resin which is deposited onto the web of open weavesupporting fabric. Simultaneously a web of microporous film isintroduced on the opposite side facing the open mesh fabric. The entireassemblage is passed through the nip of two rolls. One nip roll has acontrolled temperature that chills the molten resin and causes it tosolidify, while the other nip roll is used to control nip pressure. Thesimultaneous combination of solidifying and pressing in this nip resultsin a permanent bond between the layers of fabric and microporous filmthus forming the composite. The resultant laminated material isaccumulated onto a takeup reel. The processes for extruding a layer of apolymer onto a supporting fabric web and laminating the plies togetherare more fully set forth in U.S. Pat. No. 5,554,246 to Anwyll, Jr. whichis incorporated herein in its entirety by reference thereto.

[0016] The high temperature volatile particulate is widely dispersedthroughout the polyolefin resin through conventional methods and becomesactivated by heat and pressure during the process of extrusion. As themolten resin begins to exit the die, the activated particles volatilizeand form numerous cells created by expansion of gas within the moltenresin. The expanding gas creates both closed and open cells. These cellscause multitudinous interruptions in what otherwise would be acontinuous barrier of thermoplastic film as it is extruded from the die.These multitudinous interruptions create both micropores and/or macrovoids in the extruded thermoplastic layer providing “breathableopenings” that allow passage of water vapor throughout the composite.The molten resin becomes solid when it contacts the chilled roll at thenip. After the resin has become solidified it is no longer in a tackystate and hence “blocking” of the final accumulated roll of material isavoided.

[0017] It is important to control the size and number of gas cells inthe thermoplastic resin as it exits the extrusion die. This isaccomplished by careful control of a combination of factors includingmelt index, amount and type of volatile particulate, the temperaturesettings of the extruder, screw speed, screen pack, back pressure, linespeed and the resin thickness. An extruded thermoplastic bonding layermay also be achieved through the addition of moisture to the resin priorto the extrusion process which results in extrusions of an adhesivelayer with much larger void areas.

[0018] The bonding adhesive film may be any thermoplastic resin that hasbeen blended with any high temperature volatile particulate. A preferredresin is a polyolefin designated as NA593 obtained from Equistar. Apreferred high temperature volatile particulate is FM 3061 obtained fromAmpacet, Cincinnati, Ohio. The high temperature volatile particulate isblended with the resin utilizing equipment that is well known in theart.

[0019] The open weave supporting fabric suitable for use according tothe present invention may be any open weave sheet material that is knownto be useful for preparing reinforced laminated sheet or rolledmaterials. Examples of useful open weave supporting fabrics include, butare not necessarily limited to, high, medium, and low densitypolyethylene, polypropylene, and polybutylene fiber matts, as well asmatts made from blends of copolymers of polyethylene, polypropylene,polyester, fiberglass and polybutylene fibers. Additionally, the openweave supporting fabric may comprise glass or graphite fibers with orwithout an organic or inorganic binder. Furthermore, the open weavesupporting fabric may contain fibers made from fiberglass, polyolefins,polyesters, acrylics, polycarbonates, polyurethanes, and the like, aswell as blends and copolymers thereof. By the term “open weave” as it isused herein is meant a woven or non-woven matt of fibrous material andmay be constructed of natural or synthetic fibers and may be spunbond ormeltblown. A preferred open weave supporting fabric is a high densitypolyethylene fiber fabric which may be obtained from Amoco Fabrics andFibers Company of Atlanta, Ga. under the trade designation “CLAF.”

[0020] The resulting laminate construction material substantiallyprevents the passage therethrough of air and water, but allows thetransmission of water vapor at a rate exceeding 1 perm of water vapor.

EXAMPLE

[0021] A polyethylene resin (NA593) is blended with a high temperaturevolatile particulate (AMPACET #FM 3061) and extrusion coated at atemperature of about 400° F. onto a moving web of an open weavesupporting fabric (CLAF) at a rate so as to form a layer of resin about1.5 mil thick. The open weave supporting fabric having the resin layerthereon passes through the nip of two rolls. Simultaneously a web ofmicroporous film is introduced into the same nip on the opposite side,yet facing extruded resin upon the open mesh fabric. The one nip rollhas a controlled temperature of about 65° F. that chills the moltenresin and causes it to solidify, while the other nip roll controls nippressure to about 40 PSI. The simultaneous combination of solidifyingand pressing that occurs at this nip results in a permanent bond betweenthe layers of fabric and microporous film thus forming the composite.The resultant laminated material is accumulated onto a take-up reel forsubsequent use as a building wrap or roofing underlayment. The laminateconstruction material substantially blocks the flow therethrough ofwater and air and has a WVTR exceeding 1 perm of water vapor.

[0022] This Example may be repeated with similar success by substitutingthe generically or specifically described materials or conditionsrecited herein for those set forth in the preceding Example.

[0023] From the foregoing description, one ordinarily skilled in the artcan easily ascertain the essential characteristics of the invention and,without departing from its spirit or scope, can make various changes andmodifications to adapt the invention to various uses and conditions.

What is claimed is:
 1. A method of making a laminate composite materialcomprising the steps of: a) providing a layer of an open weavesupporting fabric; b) providing a layer of a breathable resin onto thelayer of supporting fabric, said resin layer being substantiallyimpervious to air and water and permeable to water vapor; and c)providing a layer of a thermoplastic resin blended with a hightemperature volatile particulate to be extruded, said layer ofbreathable resin and said layer of supporting fabric, wherein theresultant laminate composite material has a water vapor transmissionrate exceeding 1 perm of water vapor.
 2. The method of making a laminatecomposite material according to claim 1, wherein said open weavesupporting fabric comprises fibers of high, medium, or low densitypolyethylene, polypropylene, or polybutylene, or copolymers thereof,glass, graphite, polyester, acrylic, polycarbonate, or polyurethane. 3.The method of making a laminate composite material according to claim 1,wherein said resin comprises a copolymer of ethylene and methyl acrylateor a polyester copolymer.
 4. The method of making a laminate compositematerial according to claim 1, wherein said step of adding a breathableadhesive material between said layer of open weave fabric and said layerof breathable resin to effect adherence between said layer of open weavefabric and said layer of breathable resin.
 5. The method of making alaminate composite material according to claim 4, wherein saidbreathable adhesive is a thermoplastic film.
 6. The method of making alaminate composite material according to claim 5, wherein saidthermoplastic film is provided with a high temperature volatileparticulate extruded between said layer of fabric and said layer ofbreathable resin.
 7. The method of making a laminate composite materialaccording to claim 4, wherein said breathable adhesive includes opencell foam agents creating a non-continuous film layer between saidsupporting fabric and said breathable resin.